Separation Method Of Contributions Of Various Transmission Paths In Open-plan Offices

Open-plan offices are widely used with advantages of low cost construction and flexibility, but have distraction by speech or noise from other positions due to absence of full height panels. Existing research shows that many factors should be taken into account to achieve good speech privacy in open-plan offices and improving only one of these factors may result in little improvement, so it is important to distinguish contributions of different acoustic transmission paths of open ceiling meeting rooms in open-plan offices. Based on existing theories and experimental studies, this paper proposes an impulse response separation method to quantify contributions of various acoustic paths of open ceiling rooms sound pressure level. In addition, the proposed method is used to obtain the speech transmission index to evaluate the contributions of each acoustic path on speech privacy in open-plan offices.First, the method is verified with simulations based on the Odeon software. An open ceiling meeting room is set inside an open-plan office, whose main transmission paths are diffracting over panel, reflecting from ceiling and reflecting from ground. The sound pressure levels simulated by Odeon, calculated by theory and calculated by proposed method are similar, which confirm the reliability of the proposed method.Second, the method is verified with the experiments carried out in 3 different types of rooms. The proposed method is used to quantify the contributions of sound diffracting over panel, reflecting from ceiling and reflecting from ground on sound pressure level. The contributions of each transmission paths vary while the results agree with the physical principles, which confirm the reliability of the proposed method. The separated contributions of each transmission path are applied to calculate the speech transmission index, thus the contributions of each transmission path on speech privacy of open-plan offices are obtained.Finally, the proposed method is applied to the Fabpod, a semi enclosed meeting room located in a large indoor, to obtain the contributions of different acoustic transmission paths to its speech privacy. For this special open ceiling meeting room in the open-plan office, the contributions of the transmission paths are related to the position of receivers. For most receivers, sound reflecting from the ground contributes most to the speech privacy. Sound scattering from the walls is the second important contributor. Diffracting from the panel is another important path. The entrance is not necessarily a vital concern as it does not have much influence when the receiver is away from the entrance. Besides, sound transmitting through the panel exits but is very weak and can almost be ignored.The proposed impulse response separation method is useful for designers to reduce the negative effects of speech noise and improve speech privacy in open plan offices. The feasibility of the proposed method is demonstrated by simulation and experiments.